Vapor generator with integral superheater



A. BELL July 21, 1964 VAPOR GENERATOR WITH INTEGRAL SUPERHEATER Filed Jan. 29, 1962 3 Sheeis-Sheet 1 INVENTOR ALA/V BELL ATTORNEY July 21, 1964 A. BELL VAPOR GENERATOR WITH INTEGRAL SUPERHEATER Filed Jan. 29, 1962 v 3 Sheets-Sheet 2 -ooooom ooaoooom eoeooomnm -ooeeeoom INVENTOR AL AM 5544 ATTORNEY July 21, 1964 A. BELL VAPOR GENERATOR wrm INTEGRAL SUPERHEATER Filed Jan 29, 1962 3 Sheets-Sheet 3 on; one 000 I ocal: 006) |0 INVENTOR A Z A N BfLL ATTORNEY United States Patent 3,141,445 VAPOR GENERATOR WITH INTEGRAL SUPERHEATER Alan Bell, Cookham, Berk, England, assignor to Foster Wheeler Corporation, New York, N.Y., a corporation of New York Filed Jan. 29, 1962, Ser. No. 169,340 Claims priority, application Great Britain Jan. 30, 1961 4 Claims. (Cl. 122-34) This invention relates to vapor generators of the type used in nuclear power plants wherein the primary fluid which has been used for cooling purposes in the reactor is caused to give up heat to liquid or vapor in an indirect heat exchanger.

In such vapor generators, the primary fluid may be circulated through a vertical tube bundle connected to a pair of headers or to a tube plate disposed within the shell of the heat exchanger. In accordance with the invention, a central section of the primary fluid carrying tubes is used as a superheater, the tubes being isolated from the remainder of the tubes by trunking forming a passage for the vapor to be superheated which passage is clear of the wall of the shell so that the superheater does not cause local overheating of the shell.

An example of a vapor generator in accordance with the invention is shown in the accompanying drawings, in which:

FIGURE 1 is a perspective view of a vapor generator showing the tube bundle arrangement removed from its shell;

FIGURE 2 is an enlarged sectional elevation view of the generator taken along a vertical plane intersecting line 22 of FIG. 1;

FIGURE 3 is a sectional plan view taken along a line 33 of FIG. 2;

FIGURE 4 is a partial sectional elevational view of the generator taken along a line 44 of FIG. 2;

FIGURE 5 is a partial sectional elevation view taken along a line 5-5 of FIG. 2;

FIGURE 6 is a partial sectional elevation view similar to that of FIG. 2 illustrating an embodiment of the invention;

FIGURE 7 illustrates a further modification of the invention.

Referring to FIG. 1, the invention in brief resides in disposing a bank of superheating tubes 12 between banks 14 and 16 of U-shaped heating tubes and in such a Way as to avoid over heating of the generator outer shell. As shown, the superheating tubes 12 are encased in a trunking 18 forming a passage for the vapor to be superheated. The heating and superheating tubes are connected to parallel inlet and outlet headers 20 and 22.

FIGURES 2 and 3 illustrate the invention in greater detail. As shown, the vapor generator comprises a pressurized vertical shell 24 having a lower liquid space 26 and a vapor space 28. Contained within the shell and in the liquid space, the heating element of the generator comprises the headers 20 and 22 positioned horizontally across the liquid space and the spaced apart U-shaped banks of heating tubes 14 and 16 connected to and joining the top sides of the headers. Inlet and outlet ducts 30 and 32 are connected to the headers so that the heated primary cooling fluid from the nuclear reactor circulates from one header through the tubes to the other header and back to the reactor.

The heating element is surrounded by a shroud or baflle 34 which stops short of the bottom of the shell, as shown in FIG. 4 and defines with the shell 24 a downcomer passageway 36. The shroud also defines a vapor generating chamber 38, (see FIG. 3) surrounding the heating element in which a vapor-liquid mixture is generated by "ice the heating tubes 14 and 16. A riser 40 is positioned at the top of the shroud and defines a passageway by which the vapor-liquid mixture is led to conventional vaporliquid separators 42.

From the separators, the separated water flows down through the downcomer 36 defined by the shroud 34 and the surrounding shell 24 to be recirculated through the steam generating chamber 38 and riser 40.

The central or intermediate bank of tubes 12, the superheating tubes, are separated from the heating tubes 14 and 16 and from the vapor generating chamber 38 by the trunking or casing 18, which trunking, with the surface of the headers, completely encases the superheating tubes except for inlet and outlet openings to be described. As illustrated in FIGS. 14, both the superheating tube bank and trunking are approximately U-shaped, the trunking defining a superheating chamber and path for the flow of vapor to be superheated which conforms broadly to the shape of the tube bank.

Above the separators 42, steam dryers 44 are positioned and are arranged to discharge dried steam into a vapor space 46. The vapor space is connected by a duct 48 to an arm 50, FIGS. l-3, of the trunking 18, which arm extends approximately horizontally from the trunking in the vicinity of one of the headers 20. This dried steam passes through the trunking 18, wherein the steam is superheated, and emerges therefrom in the vicinity of the other header 22 (from a similar arm 52 of the trunking) and leaves the generator through a riser duct 54 and an outlet 56. A baflle 58, FIG. 2, is disposed in the superheating chamber to separate the incoming dried steam from the superheated steam.

FIG. 5 illustrates the manner in which the heating and superheating tubes are aflixed to the intake header 20.

It is apparent that the superheater section of the tubes, in which the temperature is considerably higher than elsewhere in the system, is completely separated from the walls of the shell, which are substantially at saturation temperature. The shell is thus protected against the effects of differential temperatures in neighbouring regions.

Instead of the headers 20 and 22, the tubes 14, 16, and 18 may be connected to a tube sheet or plate 60 as shown in FIG. 6. Also the down flow duct and riser duct may be arranged to pass outside of the shroud 34, as illustrated in FIG. 7.

For the purposes of this specification and the following claims, the term header shall be defined as a tube, chamber, tube sheet arrangement, or the like to which a series of tubes or connections are joined, and shall encompass the embodiments of FIGS. 2 and 6.

Many other modifications will be apparent to those skilled in the art. For instance the headers (or tube sheet) may be baffled, and the superheater tubes arranged, to provide optimum efficiency. Also, although the directions of flow of vapor and heating fluid in the superheating chamber are described as being parallel, opposite directions of flow may be used if desired. Accordingly, the invention is to be limited in scope only as defined in the following claims.

What is claimed is:

l. A vapor generator of the type wherein a primary heating medium at a high pressure is caused to give up heat to a fluid by indirect heat exchange comprising a pressure vessel shell; means for introducing the fluid into the shell and means to maintain a liquid level in the shell so as to form a liquid space and a vapor space therein; a tube bundle comprising a plurality of U-shaped tubes disposed within said liquid space; adjacent elongated coextensive inlet and outlet headers within the shell to which opposite ends of the U-shaped tubes are connected, said headers extending across the shell and having end portions adjacent opposing sides of the shell; means to introduce a high pressure heating medium into said inlet header, said tube bundle being substantially coextensive with said headers and comprising an intermediate bank of tubes and end banks 'of tubes on opposite sides of said intermediate bank of tubes and adjacent said shell opposing sides; trunking means encasing said intermediate bank of tubes and defining a closed flow path coextensive with and of the general configuration of the tubes of said intermediate bank; means for introducing vapor from said vapor space to said trunking means for superheating the same, said trunking means defining with said vessel shell a space which constitutes part'of the liquid space of the vessel such that the vessel shell is shielded from superheat temperature by the liquid in said liquid space; and means arranged to convey superheated vapor from said superheating section.

2. A vapor generator according to claim 1 wherein said pressure vessel shell is an upright cylindrical member having a lower liquid space and an upper vapor space, said inlet and outlet headers comprising parallel cylindrical members extending across the lower end of the shell in said liquid space.

3. A vapor generator of the type wherein a primary heating medium at a high pressure is caused to give up heat to a fluid by indirect heat exchange comprising a pressure vessel shell; means for introducing the fluid into the shell and means to maintain a liquid level in the shell so as to form a liquid space and a vapor space therein; a vapor outlet from said shell; a baffle means within said liquid space defining a vapor generation chamber and with the walls of said pressure vessel shell a downcomer passageway; a tube bundle comprising a plurality of U-shaped tubes disposed within said liquid space and within said vapor generation chamber; adjacent elongated coextensive inlet and outlet headers within the shell to which opposite ends of the U-shaped tubes are connected, said headers extending across the shell and having end portions adjacent opposing sides of the shell; means to introduce the high pressure medium into said inlet header, said tube bundle being substantially coextensive with said headers and having an intermediate bank of tubes and end banks of tubes on opposite sides of said intermediate bank of tubes and adjacent said shell opposing sides; trunking means encasing said intermediate bank of tubes and defining a closed flow path coextensive with and of the general configuration of the tubes of said intermediate bank; means for introducing vapor from said vapor space to one end of said trunking means for superheating the same, said trunking means defining with said vessel shell a space which constitutes part of the liquid space of the vessel such that the vessel shell is shielded from superheat temperature by the liquid in said liquid space; and means connecting said superheating chamber at an end removed from said one end to said vapor outlet to convey vapor from the superheating chamber.

4. A vapor generator of the type wherein a primary heating medium at a high pressure is caused to give up heat to a fluid by indirect heat exchange comprising in combination an upright pressure vessel shell; means for introducing the fluid into the shell and means to maintain a liquid level in the shell so as to form a liquid space and a vapor space therein; a vapor outlet from said shell; shroud means within said liquid space defining a vapor generation chamber and defining with said pressure vessel shell an annular downcomer passageway; a central riser in communication with said vapor generation chamber; vapor-liquid separating means in communication with said riser; said separating means being adapted whereby vapor flows to said vapor space and liquid to said downcomer passageway; a tube bundle comprising a plurality of U-shaped tubes disposed Within said liquid space and within said vapor generation chamber; adjacent elongated coextensive inlet and outlet headers within the shell to which opposite ends of the U-shaped tubes are connected, said headers extending across the shell and having end portions adjacent opposing sides of the shell; means to introduce the high pressure medium into the inlet header, said tube bundle being substantially coextensive with said headers and having an intermediate bank of tubes and end banks of tubes on opposite sides of said intermediate bank of tubes and adjacent said shell opposing sides; trunking means encasing said intermediate bank of tubes and defining a closed flow path coextensive with and of the general configuration of the tubes of said intermediate bank; means for introducing vapor from said vapor space to one end of said trunking means for superheating the same, said trunking means defining with said vessel shell a space which constitutes part of the liquid space of the vessel such that the vessel shell is shielded from superheat temperature by the liquid in said liquid space; and means arranged to convey superheated vapor from an end of said trunking means removed from said one end to said vapor outlet.

Badenhausen Dec. 14, 1943 Kopp et a1. Jan. 26, 1960 

1. A VAPOR GENERATOR OF THE TYPE WHEREIN A PRIMARY HEATING MEDIUM AT A HIGH PRESSURE IS CAUSED TO GIVE UP HEAT TO A FLUID BY INDIRECT HEAT EXCHANGE COMPRISING A PRESSURE VESSEL SHELL; MEANS FOR INTRODUCING THE FLUID INTO THE SHELL AND MEANS TO MAINTAIN A LIQUID LEVEL IN THE SHELL SO AS TO FORM A LIQUID SPACE AND A VAPOR SPACE THEREIN; A TUBE BUNDLE COMPRISING A PLURALITY OF U-SHAPED TUBES DISPOSED WITHIN SAID LIQUID SPACE; ADJACENT ELONGATED COEXTENSIVE INLET AND OUTLET HEADERS WITHIN THE SHELL TO WHICH OPPOSITE ENDS OF THE U-SHAPED TUBES ARE CONNECTED, SAID HEADERS EXTENDING ACROSS THE SHELL AND HAVING END PORTIONS ADJACENT OPPOSING SIDES OF THE SHELL; MEANS TO INTRODUCE A HIGH PRESSURE HEATING MEDIUM INTO SAID INLET HEADER, SAID TUBE BUNDLE BEING SUBSTANTIALLY COEXTENSIVE WITH SAID HEADERS AND COMPRISING AN INTERMEDIATE BANK OF TUBES AND END BANKS OF TUBES ON OPPOSITE SIDES OF SAID INTERMEDIATE BANK OF TUBES AND ADJACENT SAID SHELL OPPOSING SIDES; TRUNKING MEANS ENCASING SAID INTERMEDIATE BANK OF TUBES AND DEFINING A CLOSED FLOW PATH COEXTENSIVE WITH AND OF THE GENERAL CONFIGURATION OF THE TUBES OF SAID INTERMEDIATE BANK; MEANS FOR INTRODUCING VAPOR FROM SAID VAPOR SPACE TO SAID TRUNKING MEANS FOR SUPERHEATING THE SAME, SAID TRUNKING MEANS DEFINING WITH SAID VESSEL SHELL A SPACE WHICH CONSTITUTES PART OF THE LIQUID SPACE OF THE VESSEL SUCH THAT THE VESSEL SHELL IS SHIELDED FROM SUPERHEAT TEMPERATURE BY THE LIQUID IN SAID LIQUID SPACE; AND MEANS ARRANGED TO CONVEY SUPERHEATED VAPOR FROM SAID SUPERHEATING SECTION. 